For my desk at work, this is the DIY Universe Kit from conceptual artist, Jonathon Keats.
The uranium-doped glass marble provides a steady supply of subatomic particles. The sliver of scintillating crystal measures, or "observes", the radioactive decay, thus splitting off an alternate universe.
If you don't get the joke, which is based on the many-worlds interpretation of quantum mechanics, trust me . . . it's funny to science geeks.
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